Many inherently sensitive and specific analytical techniques are greatly degraded by undesirable components in sample matrices. For example, DNA analysis techniques such as PCR and LAMP are typically completely inhibited by components in blood. To overcome this problem, DNA is usually either precipitated, extracted into a different liquid phase, or extracted onto a solid phase and then released to clean liquid.
A convenient method to purify nucleic acid is solid-phase extraction onto paramagnetic silica particles. This allows binding, washing steps, and elution to be conducted without a centrifuge and with a small number of sample transfers. However, the samples still need to be transferred from the initial collection container (such as a blood drawing syringe or vacuum test tube) into a sample preparation tube, and then open transfers of liquid are performed with pipettes or other fluid-moving devices. The initial sample transfer and subsequent open transfers are vulnerable to external contamination, and the fluid metering and transferring equipment can add unwanted complexity. The conventional paramagnetic particle technique involves many pipetting and manipulation steps and is hard to avoid sample-to-sample cross-contamination in reusable fluidics, which would not be acceptable for medical testing due to concerns of false positives.